HVAC School - For Techs, By Techs

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks to us about refrigerator and freezer defrost strategies. Check out Dick's book HERE. In commercial refrigeration, we deal with much lower evaporator temperatures than residential HVAC. Although an evaporator temperature of 40°F may be commonplace in residential HVAC, you can expect evaporator temperatures from 25-30°F in refrigeration. Even though having ice on the coil is a negative thing in residential HVAC, it is perfectly normal in refrigeration. The purpose of defrosting is to bring the evaporator temperature above freezing to melt off the frost. We can defrost a coil in a few different ways, including a mere off-cycle defrost in medium-temperature refrigeration. When the system shuts off, the evaporator coil can start defrosting. However, if too much heat is introduced to the system, more frost can accumulate on the evaporator coil. As such, a planned defrost may be in order. These defrosts occur on a timer and turn the system off overnight. Alternatively, these defrosts may use electricity or hot gas to remove ice from the coil more rapidly, especially in low-temperature applications. Electric and hot gas defrost are common defrost types. The hot gas method generally reverses refrigerant as a heat pump does; hot discharge gas runs through the evaporator coil and melts the ice off the coil. However, hot gas is an expensive method and can negatively impact system longevity if used improperly. The electric method is cheaper than the hot gas method; this method relies on electric heat outside the coil to melt the frost from the outside. Dick also talks about: Warm air infiltration Coil-sensing thermostat controls Defrost failsafe Defrost termination "Snowing" in the box and fan delays Drain pan heaters and drain complications Paragon timers Demand defrost setups/clocks Check out RefTech HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bill and Bryan recap the 2018 AHR conference with what they learned and what you can expect to see in the HVAC/R trade in the next year. There were 2100 exhibitors who gave demonstrations and discussed products. AHR shows the real scope of the HVAC/R industry, and it is an excellent opportunity to learn more about the trade and do some networking. At the AHR conference, there were some demonstrations that may indicate a paradigm shift in the industry's best practices. For example, the AccuTools booth projected the rate of evacuation through three hoses of different diameters, including the mythical 1" hose. The visual representation of those evacuation rates showed the trend towards faster evacuations with larger hoses. More tool manufacturers may jump on the trend to make larger hoses that assist technicians and lead to better evacuations. The technology on display at AHR also testified to the fact that many more tools are integrating with our cell phones, including the CPS IAQ monitor. AHR also had a treasure trove of new technologies, including BluVac's Bluetooth-connected combustion analyzer. BluVac's branding is very science and engineering-focused, and they also fine-tune their technology to support techs in the field. Overall, AHR was a fantastic forum for people to spread information about products. In turn, Bill and Bryan had some of their product research validated and built upon. Bill and Bryan also discuss: Attaching micron gauges at the pump Professional branding Industry education Surge suppressors and melting issues The time Bill called Bryan out Engagement with HVAC educational materials Testo precision manometers and additional heads Filling the HVAC/R skills gap Increasing your value as an individual technician in this industry Building performance in the HVAC industry Internet of things (IoT) The commercial HVAC market If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast episode, Bryan talks to west-coast commercial tech Jim Loring about pneumatic controls and variable air volume (VAV) systems. People sometimes confuse pneumatics and hydraulics. Hydraulics use liquid to provide pressure; conversely, pneumatics use air to provide pressure. Pneumatic controls use a bit more energy than other controls, but they are less costly all around. Nowadays, direct digital controls (DDCs) provide greater energy savings than pneumatics. However, pneumatic controls were a precursor to the DDC technologies we use on actuators today, and they are still a prevalent technology. The air compressor is a critical component of pneumatic controls. That is because pneumatic controls require clean, dry air. Air compressors have an auto-drain and auto-dryer to help purify the air for peak performance. However, while air compressors are basic, their maintenance practices are often overlooked. Variable air volume (VAV) units vary airflow throughout the building via zones. Each zone has a damper and a thermostat. The thermostats control the dampers, which control airflow to the zone and move via actuators. In a pneumatic control system, the air pressure release or gain at the thermostat moves the dampers. Thermostats also have to bleed off some of that air via direct or reverse-acting controls. Bypasses help regulate static pressure when dampers close. Thermostats can help modulate the dampers; they don't merely open and close. The modulation occurs within a certain pressure range on a VAV system. (For example, 8 PSI would close the damper while 13 PSI would leave the damper wide open.) In addition to damper modulation, velocity controllers help control the air velocity based on signals from the thermostat. Jim also covers: Common air compressor problems Pressure-reducing valves (PRV) Restrictor tees Direct-acting vs. reverse-acting controls Heating and cooling in VAV systems Damper position If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jeremy Smith goes over floating suction and floating head refrigeration strategies. He also talks a bit more about low-ambient equipment operation. Floating suction controls developed when we started using low-pressure controls on rack refrigeration. As the electronics advanced, we developed controls that could control temperature, which impacts pressure as well. Nowadays, controls can cross data and be much more effective at controlling pressure and temperature. Suction pressure is the greatest contributor to a system's compression ratio. The higher the compression ratio, the less efficient a system is; a high compression ratio can be costly for grocery business owners or managers. Therefore, floating suction controls set the temperature exactly to what it should be based on the system's load, not lower than what the suction temperature should be. Floating head controls attempt to minimize the compression ratio from the high side of the system. The floating head attempts to maintain head pressure by matching condenser fans closely with ambient temperatures. Ambient temperature controls the floating head control's set points. These floating head controls can set the condensing temperature as low as 68 degrees (F). The main factor that prevents the temperature from getting any lower is the expansion valve. It is possible that EEV usage could enable even lower temperatures, but they have been quite problematic so far. Jeremy recommends taking advantage of natural subcooling to get the most out of your floating head strategy. These controls have to decrease capacity before they hit their targets. As such, these floating head and suction controls can be erratic and "swing" from extremes upon startup. Jeremy also covers: Energy and monetary savings Pressure differentials caused by floating head controls Expansion valves in refrigeration Superheat "floating" "Drain" leg or regulator If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bryan talks with Jesse and Nathan about setting up dehumidification for residential equipment in general. They also discuss some of the required and recommended settings on an Ecobee thermostat. On typical single-stage residential equipment, dehumidification works based on CFM per ton. We control humidity by dropping the CFM across the indoor coil and extending runtime. However, as you cool the air, you reduce its ability to hold moisture. So, you increase relative humidity through cooling. When we have achieved the desired humidity but not the desired temperature, the thermostat reduces the fan speed. Thermostats should vary the fan speed based on the call for cooling and the humidity in the air. Some systems have a dehumidification terminal; when there is a call on that terminal, the fan speed gets maxed out. Some older thermostats would display relative humidity but did not have a dehumidification terminal; these systems would merely overcool instead of removing the humidity. These systems would be very prone to freezing. Nowadays, freezing still occurs on occasion, but our newer thermostats can control their CFM per ton much better to prevent freezing. Ecobee thermostats work to integrate many different accessories. So, Ecobee thermostats try to solve every problem on a system, even on systems with supplementary humidifiers or dehumidifiers. These thermostats don't have a dehumidification terminal, but they have ACC- and ACC+ terminals for accessories, including dehumidifiers. Many technicians become confused when they think that the fan is a core element of dehumidification. Instead, the ACC terminals should be set as single-transformer, and you can choose the dehumidification option (which should NOT have the fan on). When wiring the Ecobee for dehumidification, connect the DH terminal to ACC+, remove the jumpers, set up the single-power source, do NOT dehumidify with a fan, and set "Dehumidifier Active" to "Open." If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, we cover the skills and traits needed to be the best residential service techs you can be. We follow up on the last episode's tips for getting a raise and discuss how to become more valuable as an employee. All good service techs clearly have to be able to repair and maintain systems well. Commercial and residential techs need to demonstrate mechanical aptitude. However, soft skills are what separate the good residential service techs from the excellent techs. Observational skills are imperative. Residential techs need to take a wide-narrow-wide approach to diagnosis. They must also utilize their senses to observe the ENTIRE piece of equipment. Observant techs are quite good at catching potential issues before they spiral out of control. Resourceful techs make the most of the books, manuals, and other resources they have. If they don't have a resource, they find it. Since residential service techs deal with customers, it pays for them to be pleasant with people. These people are still honest with customers, but they're positive and empathetic. The best techs are organized and keep their tools in order for maximum efficiency. Efficient techs increase their value as employees with every task. They become quicker as they become more confident with tasks. Great techs are also conscientious. They are aware of their surroundings and considerate of the customer's property and feelings. Excellent techs are also self-aware about their knowledge. They understand that they don't know everything, and they know what they have to study or search for. Finally, the best techs are all neat, clean, and communicative. Residential service techs are our industry's ambassadors, and it is important that they communicate well AND project a good image of the industry and company to the customer. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

As we ring in the new year, this episode focuses on how people in the HVAC/R trade can get a raise, promotion, or bonus without facing rejection or sounding selfish. Before you think about asking for a raise or promotion, evaluate your company. Is your company pragmatic? Does the company refuse to address conflict or let tempers run high? Do your leaders care about making decisions logically and promote people who will truly help the business? A pragmatic company makes logical decisions and respects the employees who keep the business alive. Many people want to ask for a raise when they find out that someone earns more than them or feel as though they haven't had a review in a while. People in these situations feel as though they are OWED additional pay. Here's Bryan's advice: DON'T ask for a raise, promotion, or bonus unless you have a written salary agreement that hasn't come to fruition. When you ask a leader for a raise, you make your leaders put their guard up. In general, it's not a good idea to make someone else put their guard up when communicating with them. If you want to talk to a leader about a plan to earn more money in the future, try to explain your vision of the future for the company; solve a company problem, or contribute to a leader's solution. Avoid self-assessments; talk about a plan or vision where YOU play an integral part in improving the company. Tie YOUR pay to the company's success, whether your solution addresses revenue, callbacks, or training within the organization. Overall, you have to show that you're willing to accomplish a task to earn more pay. A pragmatic business will see the value in your ideas and will be more willing to give you a raise, promotion, or bonus after you execute your plan. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, we discuss power distribution and some practical tips about three-phase, single-phase, and split-phase power. The power company generates three-phase power; a power pole transformer typically has three current-carrying conductors. Each phase of power runs at 60 Hz and generates a sine wave. That sine wave peaks and valleys in a wavy formation. Power is generated in a rotating magnetic field, so it is helpful to think of a sine wave as a variation of a circle. Transformers take high voltage and bring it down to 120V split-phase via a winding on the left, a winding on the right, and a neutral tap. The split sine waves are exactly 180 degrees out of phase; they are direct opposites, and they will intersect and both be "off" at the same time. The center is neutral. This 120V split-phase power results in 240V total; therefore, we can use them in 240V applications. Split single-phase motors require a capacitor. Three-phase power uses all three legs of power, and the sine waves are 120 degrees out of phase with each other. In three-phase power, only one wave will be "off" at any point in time. Three-phase power is a more efficient means of running motors; split single-phase power is relatively inefficient and requires a capacitor. However, reverse-phasing is a possibility and may run motors backward, causing damage. The most common type of three-phase transformer uses the wye configuration and works for 208V applications. Bryan also discusses: Wye vs. delta configuration Delta configuration high leg Start assistance and capacitors Residential vs. commercial applications Capacitor failure 277V and 480V applications Replacing single-phase with three-phase power or vice versa Three-phase condensers with single-phase air handlers If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Learn about large-scale desiccant dehumidification from the expert, Tom Peterson. Tom works with CDI (Climate By Design International). Dehumidification has several different methods and applications. Cooling is the most basic of those methods, but it has its limitations. For example, dehumidification by cooling may leave moisture on the coil and lead to freezing. Desiccant dehumidification can remove water from the air without the possibility of freezing the unit. Desiccants are crystalline structures with pores, and they remove moisture via adsorption. Water has a pressure that pushes other water molecules into those pores. Partial pressures also help force the pressures from high to low. Moisture will only come out of the desiccant upon heating the air around it. Heat excites the water molecule that has been trapped in the desiccant pore, so that molecule breaks the bond between itself and the desiccant (desorption). Commercial/industrial dehumidifiers make use of desiccants. Desiccants fit into rotors or wheels, and air passes through the desiccant rotor. The goal is to dehumidify and only dehumidify. So, no heat transfer occurs as air passes through those desiccant rotors. About 3/4 of the rotor works to adsorb moisture, and about 1/4 of the rotor works to desorb moisture. We measure moisture in a unit of weight called grains per pound of dry air (simplified to "grains"). Grains refer to moisture rather than a humidity percentage, but grains and humidity are indeed linked. Even though we attempt to reduce grains per dry air, we cannot have negative grains of moisture; it is an impossibility. Tom also discusses: Sensible vs. latent heat Grain depression Dew point Learn more about desiccants at the CDI website at cdihvac.com and their YouTube channel HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Carter tells us why compression ratio is important, what it means, why it changes so much on heat pump systems, and the effect it has on system operation. We also talk a bit more about heat pumps and their unique challenges beyond compression ratio. Compression ratio is a comparison of discharge pressure to suction pressure. A ratio of 3:1 indicates that the discharge pressure is three times higher than the suction pressure. The higher the pressure difference, the less gas you move and the less efficient your system is. The compressor has a fixed volume, but the gas's actual mass varies based on density and pressure. So, lower suction pressure results in less gas being moved. Dirty filters, coils, and other means of clogging the system can drastically increase the compression ratio. Heat pumps are especially sensitive to compression ratio changes because they move varying amounts of refrigerant depending on the operating mode. As such, charging heat pumps can be a challenge. Some heat pump manufacturers use a charge compensator to help make charging a slightly less difficult task. Heat pumps may also have coils with smaller surface areas, which can drive up the compression ratio. Heat pumps have highly variable evaporator temperatures, and refrigeration systems have highly variable condensing temperatures. Both of these highly variable conditions may indicate systems with susceptibility to high compression ratios. In the case of refrigeration systems, the metering devices are critical components for reducing keeping the compression ratios at bay. If you cannot find manufacturer literature or are working on an old heat pump, Carter recommends using airflow and temperature difference to determine how much heating the system is accomplishing. Carter and Bryan also discuss: Rheem and Ruud heat pumps Centrifugal blowers Plenum placement New inverter-driven compressors If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, Bryan talks about voltage (volts) and resistance (ohms), specifically using a voltmeter and an ohmmeter for diagnosis. We also discuss voltage drop. In many cases, Ohm's law is impractical for field usage because of the additional resistance from inductive reactance. We also don't typically measure impedance and only care about resistance on the windings. However, Ohm's law is still a valuable concept because it teaches technicians the relationship between voltage, amperage, and resistance (ohms). Ohm's law states that volts equal amps multiplied by ohms (E = I x R). Therefore, if the volts stay constant, ohms will increase as amps decrease and vice versa. We distinguish lines from loads in circuits; we say that loads are the parts that "do" something due to resistance in a circuit. There are two kinds of loads: inductive and resistive. Inductive loads generate expanding/collapsing magnetic fields, which can also cause rotational force or activate a solenoid. Resistive loads generate light and heat, so heat and resistance are related. Of course, the diagnostic tools we use (multimeters, voltmeters, ammeters, ohmmeters, etc.) also have their limitations. A voltmeter merely determines a difference in charges between two points. When using a voltmeter on a low-voltage circuit, try to plant one of your leads on the common side and take readings throughout the circuit with your hot lead. Ground is also NOT a reliable reference point for diagnosis. The point of measurements is to prove what we suspect to be true; we must understand what our data mean for system operation and what our tools' diagnostic limitations are. For example, when we ohm out contactors, we check to see if they're open. Bryan also discusses: Fixed wattage or resistance Reading between wires Meter lead placement Amperage (dynamic current/electrons) Undiagnosed shorted circuits Contact points Voltage drop and resistance Infinite ohms Wire length If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jamie Kitchen from Danfoss talks all about variable-speed motor technology. He discusses why those motors exist, what they do, and how to think differently about the future of HVAC/R. Most techs think about variable-speed motors as the X13 and ECM blowers in residential applications. Those motors can adjust their performance based on ambient temperatures and moisture levels. So, variable performance may result in better comfort and efficiency. ECM motors adjust airflow based on sensor inputs, especially dehumidification calls. The sensors may pick up both sensible and latent heat content. Sensible heat is what we can feel (dry-bulb temperature). Latent heat refers to moisture in the air (humidity, wet-bulb). ECM motors adjust their speed based on data from both, which is highly beneficial for greater comfort in the home. Human comfort is a lot more complex than feeling satisfied with a single number on the thermostat; ECM motors help control humidity and give you more leeway over selecting an acceptable dry-bulb temperature of a space. Variable-speed motors exist on the commercial side of the HVAC industry as well. Commercial HVAC equipment brings in more fresh air and is overall less restrictive than residential. A variable-speed motor can help manage the latent heat of fresh air and work as a form of air treatment. Variable-speed motors compare indoor and outdoor conditions to treat the fresh air and maintain the indoor conditions. These motors account for sensible and latent heat loads, just like the residential ECM motors, and they adjust themselves constantly. Jamie and Bryan also discuss: Capacity and heat profiles X13 motor controversy Having multiple variable-speed components in a system (compressor, blower, etc.) Sensible heat ratio (SHR) and heat load matching Complex human comfort Reheat coils Air treatment requirements If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jack Rise returns to the podcast to share some duct design facts with us and talk about his Manual D book on the ACCA website. Before we can even start thinking about duct design, we need to think about the total effective length; even before that, we also need to think about finding the critical path. The critical path is the path with the greatest resistance to airflow (from the return to supply); the fittings in the critical path contribute to the duct's total effective length. Flex duct is a controversial and somewhat complicated building material. It's common in Florida, but Jack doesn't use it in his duct designs; he can't depend on others to install it properly. Very few people tend to install flex ducts as tightly as they probably should. Noise is a problem for ducts, and takeoffs on the plenum are a significant contributor to noise issues. Instead, Jack suggests having a takeoff from the collar that goes straight into the appropriately sized duct for the desired airflow. (It's also worth noting that noise is subjective and is difficult to measure.) It's also unwise to position two takeoffs directly across from each other, as noise travels across those. The rise of indoor air quality (IAQ) products also requires us to look at duct design facts. Filtration improves IAQ but increases static pressure and can impede airflow. We need to be able to plan for IAQ products when we design ductwork. Jack and Bryan also discuss: Selecting the equipment location and position Balancing damper placement and leakage Radial systems and symmetry Plenum sizing Why panning is not great (and illegal) Why bay jumping is a bad idea Duct design vs. truss positioning Airflow in the occupied zone Check out Jack's book, Understanding Manual D, HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Nate Adams joins the podcast to describe the method behind his madness of removing gas meters and installing heat pumps in Ohio. Nate is in the home performance business, and he focuses on its intersection with the HVAC industry We typically find heat pumps in milder climates, so removing gas meters and replacing them with heat pumps is a bold move in cold climates. However, high-performance heat pumps have inverter technology, which allows them to run in colder climates without freezing over in the snow. Nate predicts an eventual switch to heat pumps from fossil fuels. Heat pumps that rely on geothermal, solar, and other renewable energy sources will be much better for the environment than natural gas and oil. Backdrafting and CO issues are also nonexistent in heat pumps. However, we also have to consider domestic hot water and other appliances that use natural gas when we switch homes over to heat pump technology. When colder climates embrace electric heat pumps, they will have to prepare for increased dehumidification needs due to the moisture in the air during the spring and fall. According to some tests run by Nate, fully electric systems model nicely and perform on par with gas furnaces in his Ohio climate. However, some people may object to heat pump installations because they prefer the comfort of gas furnaces. When you look at mean radiant temperature (MRT), surface temperature contributes most to human comfort. In that case, BTU output and load matching are what really matter, not the system type. Nate and Bryan also discuss: Equipment sizing for load conditions Split systems and backup heat Being theoretical vs. using real data ACH50 vs. CFM50 High-efficiency furnaces and combustion air Determining surface temps and MRT Startup and commissioning of high-performance heat pumps Dehumidification and reheat systems Learn more at energysmartohio.com and natethehousewhisperer.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bill Johnson is one of the great educators and writers of our time in HVAC/R. In this podcast episode, he shares some information about his career and some of his top tips on keeping systems leak-free. Bill began his work on leak-free solutions by using Glyptal on centrifugal compressors. The Glyptal would harden around leaks and seal them up. Nowadays, this is an ineffective approach to sealing leaks in higher-pressure systems. Bill got the idea to start manipulating pressures to minimize leaks with a standing pressure test for 24 hours at the highest test pressure recommended by the manufacturer. That is Bill's best practice, though it is not always feasible. Bill's rationale is that leaks become much more evident under those testing conditions. (Remember, pressurize the line set. Pressurizing the system can be a bad idea.) On top of that, Bill recommends pulling a deep vacuum and performing a standing vacuum check according to the manufacturer's guidelines. Fitting inspections are also critical; fittings may be sealed imperfectly, and they are common leak points. Check fittings with a mirror and a good light to look for imperfections and cracks. Leaks generally occur in piping, not the equipment itself. Moreover, vibrations and corrosion generally cause leaks. Begin a leak inspection by leak-checking the gauge ports BEFORE attaching gauges. In general, inspect the entirety of the equipment with your senses before attaching gauges. When leak-testing with soap bubbles, make sure to use one that doesn't need to be washed with water, as water can lead to corrosion. (We recommend Refrigeration Technologies Big Blu.) Most of all, don't leave a job until you find a leak or confirm that the system is leak-free! Bill also discusses: Being an HVAC teacher Critical charge leak detection Pressurizing with nitrogen Misleading leak detection equipment Torque wrenches If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jim takes us all the way through the history of furnaces, from the Stone Age when he was a child to modern modulating condensing types. The goal of a furnace is to move heat, so a furnace uses heat exchangers to facilitate heat transfer. Furnaces have primary and secondary air. The primary air goes through the burner, and the secondary air goes around the flame and is pulled in around the heat exchanger inlet. So, the flame's heat creates a draft that pulls air in. Natural gas and oil (LP/propane) furnaces are common nowadays, but we initially burned wood and coal in furnaces. The first gas furnaces came into existence by modifying coal, not from the gas lines we see nowadays. Long ago, the flue gases were also exhausted to the basement; CO poisoning was less of a concern back then, as combustion was usually complete. Burning the building was a much more severe risk. The first "gas crisis" in the 1970s forced us to focus on gas furnace efficiency. In that time, we developed spill switches and retrofit kits that converted furnaces over to spark ignition. In the 1980s, we came out with the draft-induced 80% furnaces we see nowadays. We also eliminated standing pilots and draft diverters. Even though the appliances became more efficient, we didn't actually burn the gas any more efficiently. So, despite the technological advancements we've made over the years, we don't actually burn gas any more efficiently than we did in the 1930s. However, our modern furnace technology has eliminated standby losses, controlled ignition, and focused on the role of latent heat in combustion. Jim also discusses: Flame color and types Draft hoods and diverters Products of complete combustion Excess air: a double-edged sword Natural ventilation Efficiency percentages Furnace testing and ratings Turbulators Modulation If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

This podcast episode on electrical circuits is a class recording. In it, Bryan discusses transformers, ground, common, and line vs. load sides of a circuit. Transformers use induction to pass alternating current signals to electrical appliances. Alternating currents (AC circuits) are tricky because the current switches direction each time. Therefore, the current flow is difficult to visualize because the direction keeps changing. Electrons naturally want to go to the other side of the transformer, not to ground. So, we have to connect both sides of the transformer to ground to send electrons to ground. (In this case, ground refers to the metal body of equipment, not the earth.) A "short" is an undesigned path, typically taken at high current due to low resistance. The high current can blow fuses and cause equipment failure. Therefore, we connect to ground to prevent that high current from taking paths that will cause equipment failure. The part of the circuit that we call "hot" is on the line side of the switch. That part is the line that goes into the switch. The part of the line that leads from the switch to the load is called the load side. After the load, we have "common" or "neutral." When common is connected to ground, it will be electrically the same as ground. However, it's worth noting that "common" can mean several different things in electrical. (Typically, we call common "L2" in high-voltage circuits with multiple phases, "neutral" in 120v circuits, and "common" in low-voltage circuits.) Bryan also discusses: The downsides of memorizing wire colors for making connections "Common" misconceptions Switch types in electrical circuits Thinking of connections as a switch and load Various terminals and wires If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In HVAC work, we deal with quite a few electrical components. But where does electricity come from? Why do electrons move? In this podcast episode, we talk about differential charges, sine waves, and some voltage measurement basics. A large chunk of electrical theory is centered on electron movement. We get electrons to move with differentials in charges or energy states. Nature tends towards equilibrium, so electrons will move to restore a state of balance. A battery or transformer does not create energy; they create energy imbalances that cause electron motion to occur. Alternating current (AC) creates a differential by reversing the direction of current several times per second. Transformers and motors use AC power and inductance to drive HVAC systems. When testing with a voltmeter, you're looking for a difference in charges. So, the probe placement matters. When you have no difference in charges, no electrical work is being done. Most of the power we use comes from power plants. At these power plants, rotating magnetic fields generate the power we use. Power generated through magnetism creates a sine wave. A sine wave is a variation of a circle; the wave goes up and down in a cyclical pattern. So, you can look at sine waves and determine exactly how legs of power are out of phase with each other. For example, single-phase power comes in and splits at the transformer, creating an opposing sine wave that is 180 degrees out of phase with the power leg (when one wave peaks, the other valleys). There is also some confusion surrounding "neutral" and "ground." Ground is merely a conductor for safety reasons and has nothing to do with electrical operations; the ground does not generate electron movement. Neutral is NOT the same thing; neutral is a circuit conductor, but we usually connect it to ground. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Do you think of the building envelope as a duct? Do you test it? In this podcast episode, Joe Medosh talks to us about envelope testing and why it's the future of building health and comfort. The building envelope is the largest duct in the entire home. However, so many HVAC techs forget about it; they attempt to optimize comfort in the HVAC system and ducts, not the home itself. Techs use Manual J and S, but they don't use the infiltration rate in their calculations. Infiltration in the envelope is a major culprit of discomfort in the home, especially through and around windows. We use blower doors to determine leakage. During the blower door test, we depressurize the home by a pressure difference of -50 Pa, and we can then calculate the air changes per hour by taking the CFM, dividing it by the volume, and multiplying that number by 60. The pressure pan is another tool that we use to determine leakage. Pressure pans are semi-quantitative tools that help you figure out where leaks are coming from; you won't find out how much CFM leakage you have, but you will find out if there is CFM leakage. The commercial HVAC industry has already used "fresh air" in buildings via economizers. However, the residential HVAC industry does not bring fresh air in via the HVAC system. Joe proposes solutions to seal homes but allow fresh air to enter the home in a controlled manner; when we bring that fresh air in, we could implement dehumidification measures to avoid fungal growth. Joe also discusses: Windows and energy savings myths Measuring volume in the home Common sources of leakage in the home Gas appliances and combustion/CO risks in tighter homes Outdoor air and retrofit applications Backdraft Balancing ventilation Check out Retrotec at retrotec.com or purchase Retrotec products from TruTech Tools at trutechtools.com/retrotec. (Use the code "getschooled" at checkout for a discount!) If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Ductless expert Jesse Claerbout talks about his best maintenance practices for ductless air conditioners and heat pumps. This episode is part 2 of the two-part series. Ductless outdoor units tend to have clean condensing coils. The only real issues are grass clippings (and cottonwood, in some locations). which typically don't affect performance too sharply. Jesse likes to clean outdoor units with plain water; he does not use cleaners. Drain cleaning is a little more involved than condenser cleaning. When cleaning a gravity drain, Jesse uses a shop vac to get rid of standing water. He does not run water through the drain line until after he begins reassembling everything after cleaning. Three main lines need to be insulated: the suction line, expansion line, and drain line. A proper ductless maintenance procedure will include checking the state of those lines' insulation. Condensate pumps can be a necessary evil in ductless unit maintenance. The cleaning procedure is straightforward, but it requires a lot of work and leaves plenty of room for techs to cut corners. Much of the difficulty comes from exposing the reservoir, which is the component that truly needs cleaning. You can clean it from the poly-tubing, but you must use a shop-vac to clean it thoroughly. When you finish, make sure that the blower wheel sounds right and that no parts are rubbing against each other. Let the unit run for 15-20 minutes before taking line temperatures so that all the parts can dry. Check the charge (preferably without gauges), air temperature split, and your amperage to make sure that the unit works as it should. Overall, the most important goal of ductless maintenance is to establish a cleaning regime that works for your business and the customer. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Ductless expert Jesse Claerbout talks about his best practices for maintaining ductless air conditioners and heat pumps. This episode is part 1 out of 2. Ductless maintenance can be a bit more extensive than regular split system maintenance. Ductless filters are plastic; they are not high-MERV and can simply be washed off with water. Customers can clean their own filters with nothing but water from a hose or sink. Blower wheels are a bit more challenging than filters; the blower wheels are long, have small cups that are prone to buildup, and carry an electrostatic charge. Due to the blower wheels' challenging nature, technicians require special training to deal with the additional labor, and customers require special education. As such, we at Kalos charge for special blower wheel maintenance. We pull the blowers from the systems and clean them (though the process of getting a blower wheel off the blower shaft is complicated). You can wash the blower wheel outside with a safe cleaner; make sure the wheel is dry when it goes back inside. Removing the blower wheel gives you full access to the drain pan. During a ductless maintenance procedure, remember to clean out the drain pan thoroughly with a safe cleaner. If you clean ANY component indoors, use a drop cloth, especially if you're cleaning on carpet. We clean evaporator coils and the housing with spray bottles (preferably) or pump sprayers. Clean WITH the grain, not against it, and use only water or mild, non-toxic cleaners. A botanical cleaner works well, especially for customers who may have allergies. Rectorseal also has a cleaning kit (Desolv) that comes with a good coil cleaner, a cleaning bib that surrounds the ductless unit, and a pump sprayer. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, we cover some common misconceptions about run capacitors, some easy ways to test them, and some tips on working with them. A run capacitor is a power storage device; it contains oil to dissipate heat and some thin metal plates wrapped in a spiral. Capacitors also contain plastic insulation between the metal plates to keep the power separate; electrons should NOT cross the insulation, and there should be a charge difference between the plates. Current also does NOT flow through the capacitor; capacitors merely store and discharge power. Capacitors also do NOT boost voltage. You may notice higher voltage between terminals, but the capacitor is not involved in that voltage boost. You see that voltage increase because of the inductive motor's back EMF. Back EMF only occurs on systems with a running motor. On a single-phase PSC application, the run winding is the primary, and the start winding is the secondary. A run capacitor that is too large will draw more current on the start winding. You may see a slight drop in overall amperage on the common wire, but large capacitors increase the current on the secondary winding. The start winding is not designed to carry excess current. Connecting capacitors in series REDUCES capacitance. Therefore, most of the time, we connect capacitors in parallel. Many electrical circuits nowadays are connected in parallel (compare to Christmas lights, which are connected in series). Bryan also covers: Capacitor basics (terminals, microfarads, etc.) "Common" confusion Capacitance and current relationship Start capacitors and potential relays Hard start kits PTCR products Series vs. parallel capacitors Testing capacitors (in the circuit, under load, with a capacitor tester, etc.) Calculating capacitance and evaluating capacitance ratings If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

James from Rectorseal talks about the IMC codes relating to tamper-resistant caps and why you may consider installing them now. Tamper-resistant caps, also known as locking refrigerant caps, fit on refrigerant ports to prevent unauthorized access. Even though these caps can RESIST attempts to tamper with the equipment, they are not (and cannot be) fully tamper-proof. Many new construction companies used to put the caps on ONLY to pass inspection; they then take the caps off to reuse them several times. That's an inhalant abuse risk, and it's also a liability issue for other contractors who service the equipment. So, the IMC requires locking-type, caps to be fastened to the equipment after charging or recovery. Unfortunately, it's impossible to enforce the code, even as it currently stands. Moreover, many technicians want manufacturers to make their equipment easier to service. Components like tamper-resistant caps make it harder to service equipment. Almost no standard tools can remove those caps, and you will need special tools for tamper-resistant cap removal. The code, however, does not define what a "tamper-resistant" cap is; a key could fall under that umbrella. However, tamper-resistant caps are still worth considering because they prevent inhalant abuse. Inhaling refrigerants is a gateway for harder drugs, including heroin. Even though tamper-resistant caps may not stop adolescents from doing drugs at all, we remove our industry from that controversial subject. It is also a good idea to give your system caps that make it harder for people to steal refrigerant, especially as refrigerant prices rise. James also discusses: The purpose of code commentary Inhalant abuse prevention Code compliance Built-in vs. added components required by code IMC vs. AHD Explaining tamper-resistant caps to customers Check out Rectorseal's Novent refrigerant caps HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Many techs know just enough about economizers to bypass them. In this podcast episode, Jerry Eavenson and Bryan talk about the basics of what an HVAC economizer is and how it functions. Economizers typically work on the air side of package units and help pull fresh air into a structure. Economizers are almost exclusive to commercial HVAC. Climate also plays a role in their usage; you will not find many economizers in hot and humid places like Florida. An economizer is generally an energy-saving device that brings fresh air into a building if it is of a higher quality than the return air. These economizers determine if the outside air is better than the return air via enthalpy controls. Enthalpy controls evaluate the humidity and temperature of the air. When you set up an economizer, you can easily go wrong if you don't understand the sensors that are involved in the setup. Many economizers have dry-bulb or enthalpy sensors (wet-bulb), and these sensors are not interchangeable. You typically have to know the model number to differentiate the two types, but the model information is readily available on the internet. Typically, your differential set points will depend on your climate zone. You may come across fixed-enthalpy or differential controls. When it comes to economizers, acquiring documentation is the best move. As with all types of HVAC equipment, reading the manual is the key to understanding what an economizer does. Jerry recommends identifying the controls, sensors, and functions of the equipment. Economizers may vary greatly across models within a manufacturer (let alone across manufacturers). Jerry and Bryan also discuss: Heat loads of commercial spaces Variable frequency drives Sensors Economizer setup Honeywell Jade Cooling stages Controls Dehumidification-only application possibilities Return duct sizing Climate zones If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Dan Holohan is the father of modern steam heat training. This episode is a narration of his in-depth steam article "A Steam Heating Primer" from HeatingHelp.com. Read that article HERE. Check out more about Dan's work at heatinghelp.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, Bryan talks with legendary Hydronics author and trainer Dan Holohan about the history of steam heating and some practical applications of old ideas. Recently, Dan has been working on more novels, having published two of them over the past few months. Steam heating is a "lost art" nowadays; it has become increasingly uncommon and has been disappearing since the Vietnam War. Many people who understood steam heating either retired or died after the Vietnam War. Many elements of steam heating are difficult to understand or surprising. (For example, steam pressure has a surprising relationship with velocity: low-pressure steam moves through piping much more quickly than high-pressure steam.) So, Dan Holohan is on a mission to revive that knowledge and teach the newer generations about the lost art. There are many older steam heating systems still operating today, especially in the older large buildings in New York. Dan learned a lot about steam heating when working on these old systems and optimizing them. Most of the time, he optimized those systems by removing unnecessary accessories, not adding components like steam traps. Many old boilers used coal as a heat source. Nowadays, many old boilers have been fitted with conversion oil burners with thermostats, but they are still piped for coal. Some systems now have multiple risers or massive vents on the main riser to prevent the thermostats from getting too hot too early and satisfying the thermostat too early. We call that master venting, reducing pressure and allowing steam to move very quickly and efficiently. Dan also discusses: The 2-PSI standard Transportation metaphors for BTUs in steam Harmful renovations for old boilers Replacement vs. restoration mindsets Gaps in steam boiler education Monopolizing the market if you HAVE the education Boiler piping and venting Two-pipe vs one-pipe steam Find out more about Dan and hydronic heating at HeatingHelp.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

This special podcast episode focuses on the tragic life and times of Spark Ranger Roy Sullivan. Roy Sullivan was a park ranger who was born in Virginia in 1912. He grew up in the 1920s when the mining industry was in full swing and had scrapped up the beautiful mountain landscape. In 1935, Shenandoah National Park was founded, and Roy decided to become a park ranger. He wanted to help restore the land and protect it from human destruction, such as the mining industry. One of Roy's duties was to scope out the forest on the new fire lookout tower. That new tower had yet to have a lightning rod installed. One day, a lightning storm approached while Roy kept watch, and lightning struck the tower. Roy survived the strike, though he was badly burned in the incident. In July of 1969, Roy encountered lightning once again. That time, Roy was driving a car. Although many people believe that the tires are insulators, most people are protected from lightning by the Faraday Cage effect; the current travels through the metal around you until it reaches the ground. Roy, unfortunately, forgot to close his window and had a lightning charge from a nearby tree strike him through the window. Roy got struck with lightning yet again while doing yardwork a little while later after a transformer was struck by lightning. He was allegedly struck by lightning several times after that, including on a fishing trip where he ALSO had to outrun a bear after getting struck by lightning. However, even though Roy had the scars, these lightning strikes are unconfirmed. Sadly, Roy died by a[n allegedly] self-inflicted gunshot wound. However, the legacy of the Spark Ranger continues through his ongoing world record for "Most Times Struck By Lightning." If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, Bryan and Jamie talk about the electronic expansion valve (EEV). Bryan and Jamie describe how EEVs work and the reason they exist. In the process, the hosts also review a wide range of metering devices. We made this podcast to address the rising demand for EEVs in the aftermarket element of the HVAC business. Like the TXV, the EEV is a metering device. Metering devices create a pressure drop as refrigerant moves from the liquid line to the evaporator. Traditional refrigerators typically use capillary tube metering devices because they require a constant temperature and operate in a fixed temperature environment. However, TXVs are a bit more variable but open linearly and are dictated by a minimum stable superheat value. EEVs are also variable, but they can influence the superheat more directly; the superheat always exceeds the minimum stable superheat. Therefore, EEVs can increase efficiency by reducing the evaporator temperature and compression ratio by increasing saturation temperature. Even though EEVs dominate the grocery refrigeration market because of their head pressure control, we can use them in residential HVAC too. The EEV controls superheat more precisely than a TXV, and their algorithms can maximize efficiency and fill the evaporator coil with the most refrigerant possible. There are two types of EEVs: the pulse-width EEV and the stepper motor EEV. The stepper motor has "steps" to modulate the degree to which it opens or closes. The pulse-width EEV either opens or closes, much like a solenoid valve. Bryan and Jamie also discuss: Hot pull down Ideal compression ratios and efficiency Minimum stable superheat Compressor cooling accessories Downsides of oversizing TXVs Evaporator superheat vs. suction superheat Technological advancements for EEVs, especially for Danfoss EEVs Less obvious advantages of EEVs over TXVs If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast episode, trade school student Chris Caldwell interviews Bryan about trends in the HVAC industry, his business, and the future. Chris works in the HVAC business as a service tech and attends trade school in Alabama. New trends include spending more money on testing instrumentation. Nowadays, there is a greater reliance on test instrumentation to produce accurate measurements. Diagnostics have certainly improved over time. On top of that, Bryan sees the industry's potential to improve other practices like evacuations. Customers have paid more attention to indoor air quality recently, and that trend is likely to continue. There is a new emphasis on comfort over energy efficiency, especially in humid climates like Florida and Alabama. As such, HVAC techs can expect an intersection between the HVAC industry and the building science industry. Customers also enjoy having integrated controls, such as thermostats that connect to wi-fi. However, some service companies and manufacturers have focused too much on shiny new technology. Bryan owes this phenomenon to the "sales-first" business model. He would prefer to see techs and manufacturers focus on basic serviceability. As such, Bryan would like to see an emphasis on creating thorough solutions to problems instead of seeking quick fixes. In the future, Bryan hopes to see further development of tools like measureQuick. He would love to see better data collection practices. He would also like to see more unified communication protocols between appliances. Bryan and Chris also discuss: Solar solutions Human comfort and IAQ Communication between techs in the digital age New ASHRAE outdoor air standards "Sales-first" business models and the skills gap How to make the HVAC industry appeal to the new generation How to find fulfillment and validation in HVAC work If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, Chris Reeves joins Bryan to discuss filter driers, including suction driers, liquid driers, core driers, different media, and basic applications. Filter driers are simple components, but they have plenty of room for misunderstanding within our trade. We refer to Parker-Sporlan Bulletin 40-10 throughout the podcast, and you can read that bulletin HERE. Above all, filter driers act as filters that prevent debris from reaching the expansion valves and destroying them. As such, the best place to install a liquid filter line drier is as close to the expansion valve as possible. These filter driers also catch and hold water from the system; they minimize moisture to keep HVAC systems functioning properly. Filter driers also catch and remove acids from the refrigerant circuit. A filter drier and its desiccants CANNOT remove non-condensable gases. However, filter driers should NOT be the primary method of removing moisture. Proper evacuations with deep vacuums should be the main method, as filter-driers are limited in their moisture removal capacity. You also don't want to use a filter drier that has been exposed to atmosphere any longer than a few minutes; the drier has had time to collect moisture and will be less effective. Each time you open up a system, removing the filter drier is the best practice. We use biflow filter driers on heat pumps. The refrigerant can flow in both directions; a check valve directs the flow, so the flow always goes through the core and filter pad the same way, regardless of operation mode. Suction line filter driers are for older HVAC systems with issues. You'll want to install them close to the compressor for maximum protection and watch the pressure drop across the drier. We also discuss: Temperature control Overheating driers and exposing them to heat HH-style filter driers (with activated carbon) System sizing as a consideration Burnout and contamination If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today's podcast, Bryan covers the four basic gas laws and how they apply to you as an HVAC technician in the field, not just in theory. Remember, when dealing with pressure, you must convert the units to PSIA, not just PSIG. To do that, you merely add 14.7 to your gauge pressure. In every equation, the "1" indicates an original value, and the "2" indicates a new value. The simplest of the gas laws was discovered first, Boyle's law. The law states that there is an inverse relationship between absolute pressure and volume. When a gas's pressure increases (such as via compression), you decrease its volume. Inversely, when you decrease a gas's pressure, that gas will expand, and its volume will increase. Mathematically, the law looks like this: P1 x V1 = P2 x V2 Charles's law focuses on volume and temperature. This gas law states that volume and temperature rise or fall together so long as the pressure stays the same. You can mathematically describe the law with the following equation: V1 / T1 = V2 / T2 The general law of a perfect gas combines Boyle's and Charles's laws. You can mathematically describe the law like this: (P1 x V1) / T1 = (P2 x V2) / T2 As HVAC technicians, we should care about the gas laws because our pressures and volumes will change as temperature changes throughout the day, such as when doing a standing pressure test with nitrogen. Nitrogen is a relatively non-reactive gas, so it will follow the gas laws and won't condense to a liquid or react with other chemicals. Dalton's law is the final law, and it states that the combined pressure of all gases in a closed space is equal to the sum of the individual gas pressures. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Alex Figueroa is a VRF and refrigeration tech in Puerto Rico, and he talks to Bryan about his work and specialized experiences. Since Mitsubishi is a forerunner in the ductless industry, many of the units that Alex has worked on are Mitsubishi units. Alex works on lots of ductless mini-splits and VRFs in central air in commercial buildings. He typically works on VRF units that have ceiling cassettes or fan coils. Some VRF units also have branch boxes with electronic expansion valves (EEVs), and those components help distribute refrigerant flow. These systems have expansion lines, which some technicians may confuse for liquid lines. As with other large commercial HVAC units, oil is also a concern in VRF systems. Smaller-tonnage systems have large accumulators, but larger systems may also have large separators. Some of these systems are large and may contain 200-300 pounds of refrigerant. Unlike many other HVAC units, these systems have an electronic interface that indicates superheat, subcooling, and other criteria that can help with charging and troubleshooting. (Techs can, however, hook up gauges at the condenser, but the practice is not often necessary.) When you open up a VRF system for the first time, you will see lots of solenoids and other components that resemble refrigeration parts. Therefore, Alex felt that his experience as a refrigeration technician benefited him as he began working on VRFs. Like heavy refrigeration (especially grocery refrigeration), VRF systems may have several compressors and refrigerant circuits in a single system. Digital scrolls are common compressor types for these systems. The greatest maintenance issues with VRFs deal with are dirty evaporator coils and filters. In Alex's experience, the electric controls are the most commonly failed component. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

What do you need to know to walk up and fix a VRF or ductless system? John Chavez, longtime VRF/ductless pro, covers his approach to ductless and VRF diagnosis in Part 2 of this podcast. (Listen to Part 1 HERE.) If you believe that there is a component failure, you'll want to check the voltage going into the unit. You'll want to pay special attention to the board and see where power is going in and out. In other words, pay attention to your inputs and outputs on the board and pay attention to the documentation in the manual. Make sure you have a quality voltmeter on hand. Another potential electrical issue occurs when the board blows out entirely. When that happens, you'll have to watch the input voltage and be mindful of the utility quality and local geography. Utility companies WILL NOT admit if they are part of the problem, so it is good for a technician to ask about the property and utilities to study the history of the unit and the location. Watch your discharge air temperatures and make sure they perform correctly under AHRI conditions (the standard is 95 degrees outdoors, 86 degrees indoors); should have 40-50 degrees coming out of the discharge of the ductless unit. Pipes may even get as cold as 37 degrees before discharge protection kicks in. To sum everything up about VRF diagnosis, you'll want to do whatever you can to find the root cause; don't be a parts-changer. To consider all possibilities, you must take your time to understand the unit. We also discuss: Lightning strikes and power surges Determining delivered capacity Critical charge Electrical/controls terminology Building science, thermal envelopes, and VRF performance Sensible and latent heat loads Inverter-driven compressors Resources Computer Room Application Formula Ductless Steps Friedrich Service Form Seven Common Install Answers If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

This episode covers some basics of matter that relate to HVAC/R. These basics include mass, weight, and volume. There will also be some talk of specific gravity and specific volume. Matter and energy are the building blocks of the HVAC industry; we move matter around and transfer energy. Matter refers to anything that exists and takes up space, including all solids, liquids, and gases. We use three means of measuring matter: volume, mass, and weight. Volume refers to how much space an object occupies. Even though we use mass and weight interchangeably, they mean two different things. Mass refers to the amount of matter an object has, and weight is the force exerted on an object by gravity. Density is a mass-to-volume relationship. Density comes into play when items float or sink in water, and it is a component of specific gravity. Specific gravity does not have an absolute unit of measure; it merely compares an object's density to water. For example, propane has a specific gravity of 1.5 in comparison to air and would sink. Conversely, natural gas has a specific gravity of 0.6-0.7, meaning that it would float in air. Specific volume is NOT relative; we use a set unit for it, typically cubic feet per pound. The cubic feet of air per pound changes with temperature, humidity, and barometric pressure. So, "standard air" isn't a fixed value. All gases can be compressed and can be affected by temperature much more easily than the other states of matter. Specific volume is important because it helps us determine the amount of refrigerant we can safely put into a recovery tank; you must know the difference between the specific volume of water and the refrigerant you are using. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

What do you need to know to walk up and fix a VRF or ductless system? John Chavez, a longtime VRF/ductless pro, explains his approach in Part 1 of this podcast. You CANNOT have a haphazard approach to installation or service. The best thing you can do is respect VRF and ductless technology for what they are. When you take the time to understand the equipment and the processes at work, you will be successful. The best thing you can bring to a job is patience. Unlike on typical split systems, gauges should NOT be hooked up to a ductless or VRF system unless they are absolutely necessary. Gauges may introduce contaminants into the system, and they may cause more harm than good if techs use them when they are unnecessary. Superheat is rarely a useful diagnostic reading for mini-split and multizone systems. However, superheat and subcooling are readily available readings that may be useful for diagnosing VRF systems. Diagnostic work requires detective work; ask questions about the system history to see how it has performed in the past. Involving owners in the repair process is a good way to build a relationship while understanding the problem better. Like split systems, dirty coils and air filters can severely compromise a VRF/ductless system's performance. So, try to make sure filters and coils are all clean during diagnosis. The fins of evaporator coils can get especially dirty and should be cleaned. Some ductless systems can be cleaned in place. Be sure to take down the model and serial numbers of the system. If you need tech support, you MUST have those numbers to be as specific as possible. Service and installation manuals are also useful tools for diagnosis (yes, we know that some techs are allergic to reading). However, don't over-rely on the error codes. Resources Computer Room Application Formula Ductless Steps Friedrich Service Form Seven Common Install Answers If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Watch the sequel to this podcast episode HERE.

Frank Besednjak talks about proper communication in conflicts between techs and managers. He also covers the potential problem with inexpensive air conditioning maintenance specials. When it comes to communication, Frank is a proponent of honesty and straightforwardness. However, he understands and appreciates the fact that people have different communication styles. He encourages people to write down their ideas, whether those ideas benefit the company, themselves, customers, etc. Frank encourages managers to set up an email or text line for people to input their ideas via written media; the leaders should make employees feel empowered to become part of the solution. The difference between a committed and complaining employee will become clear in the way that they communicate suggestions. Cultivating positivity in the business starts with future-oriented leaders. Managers who focus on the past allow negativity to breed, especially when they fixate on poor performances in the past. Frank also suggests that managers take the "good in public, bad in private" approach when discussing employee performance. The point is to find solutions, not make employees feel bad. Some PM "specials" include the infamous $89-tune-up. Some techs use these PMs as opportunities to push products and make sales. Frank believes that the pricing is not the issue; dishonesty about the tune-up's intentions is the issue. Sadly, these "specials" are often scams, but they still work for bringing in business. Some companies even do "classes" that are truly sales meetings; those meetings teach techs how to upsell and push products. This practice also opens the door for honest, skilled techs to be replaced with salespeople who do not fix units as they should. Frank recommends implementing a good pricing strategy that lets customers make their own decisions. Then, you will attract business honestly. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Carter Stanfield, a co-author of Fundamentals of HVACR, talks about the entire refrigeration circuit. He also explains how to read and plot a pressure-enthalpy diagram. The refrigeration circuit has four main components: evaporator, compressor, condenser, and metering device. When teaching, Carter likes to explain that boiling is a cooling process and condensation is a heating process. He describes saturation as the breaking point at which liquid refrigerant can no longer hold more heat (in the evaporator). The superheated vapor from the suction line then enters the compressor; the compressor adds even more superheat. So, the discharge line has very superheated vapor. In the condenser, saturation occurs when the vapor cools to the point that it can no longer hold more moisture; the temperature stays the same until the refrigerant becomes entirely liquid. Subcooled liquid travels to the metering device via the liquid line. The metering device reduces the pressure of the refrigerant and feeds the evaporator. However, some flash gas occurs and helps drop the temperature of the remaining liquid. A pressure-enthalpy diagram illustrates the refrigerant's changes in and out of the saturated state as it moves through the refrigeration circuit. The chart looks like a curved dome, and saturated states are inside the dome. Pressure is on the y-axis, and enthalpy is on the x-axis. Pressure is a logarithmic arrangement; a linear arrangement would be impossible to plot. The bottom of the chart shows low pressures, and the top shows high ones. Enthalpy is the heat content of the refrigerant. We express it in BTUs/lb. When you plot one of these diagrams, you can start with four lines and readings: high and low-side pressure, suction line temperature into the compressor, and liquid line temperature into the metering device. You will end up drawing a parallelogram shape on the chart. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

James Bowman talks to Bryan about leak sealant products, including RectorSeal's Leak Freeze product. James talks about how sealants work, what happens when they don't work, and how to be open-minded without being gullible. Leak sealants must not react adversely with the components inside a system (oil and refrigerant). Just as mineral oil caused some issues with O-rings, POE oil has additives that cause acid to form on the system. RectorSeal's Leak Freeze is technically an oil that can work with the oil and refrigerant that already exists in an HVAC system. Leak Freeze is a high-performance lubricant that creates a soft bond around a leak and doesn't clog the system. Many refrigerant-based polymer leak sealants are hard chemicals that technically succeed at sealing leaks. However, these leak sealants are prone to clogging a system when they clot together (via flocculation). If a sealant has hazard pictograms, then there's a good chance it is a refrigerant-based sealant that creates polymers. When selecting a product, there will always be pros and cons with each product category. There are cases where each type makes sense; you must know your customers, business, and employees to determine the best choice for each unique situation. In a test that Bryan performed with Leak Freeze on a rubout leak on the high side of the system, he noticed that the sealant managed to stop the leak while the system ran. Then, the system shut off. After that, there was only a slight leak. Generally, the product was meant to work better on formicary corrosion on the low side, but it still proved to be effective at sealing a leak in a challenging location. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks about making the switch from A/C to refrigeration. Dick Wirz is an advocate for using rules of thumb, which is a controversial position. However, rules of thumb are an excellent way for A/C techs to dip their toes into the refrigeration world. Rules of thumb are less likely to overwhelm technicians than the exact technicalities of certain readings and measurements. Some prime examples of using rules of thumb in air conditioning are condenser split, evaporator split/TD, subcooling, and superheat. Those all have relatively neat "rules of thumb" that don't vary too much. (30-degree condenser split, 35-degree evaporator TD, 10-degree subcooling, and 10-degree superheat.) On medium-temperature refrigerators, a common rule of thumb is a 10-degree TD for a 35-degree box with an evaporator running at 25 degrees (35 - 10 = 25). On low-temperature applications, the box temperature is -10 degrees. You still have the 10-degree TD, so the design conditions for the evaporator would be -20 degrees (-10 - 10 = -20). The pressures will vary across refrigerants, but the temperatures WILL REMAIN the same as the rule of thumb. Ice is an alarming sight for residential technicians. However, commercial refrigeration technicians will occasionally see frost or ice under perfectly normal circumstances. Frost merely indicates that the temperature of a pipe is below freezing. Ice alone does NOT indicate floodback. In commercial refrigeration, the fans run all of the time to defrost the system (even during the off cycle). However, in freezers (low-temperature refrigerators), hot gas or electric defrost is required. Dick also talks about: Subcooling vs superheat in diagnosis R-410a pressure confusion Reach-in and walk-in refrigerators Medium and low-temperature refrigerators Defrost controls Common issues in commercial refrigeration If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Camron Conlee joins the podcast to give us an introduction to ammonia chillers. He also explains what it's like to work with a poisonous refrigerant. The California division of TDI Refrigeration, where Camron works, primarily works on ammonia systems. We often see ammonia refrigeration in cold storage and food processing; ammonia refrigeration is usually in industrial applications away from the public. Ammonia is more hazardous than CO2 and other refrigerants because it is toxic. When working on ammonia chillers, the most important thing is to keep the ammonia inside the pipes. You may even need to wear full-face respirators and personal monitors when working on potentially leaky ammonia systems. Ammonia chiller oil systems are a bit different from R-22 systems. Oil separation is important in both ammonia and R-22 refrigeration, as ammonia systems typically use coalescing separation methods to isolate oil from the refrigerant. However, the oil generally doesn't mix with ammonia as readily in the first place. Some systems rely on pressure differentials to move liquid, and others use pumps to move liquid ammonia into the evaporator. Preventive maintenance on ammonia systems is quite similar to PMs on other types of refrigeration systems. Compressors are also important components that require occasional maintenance. Like many other commercial refrigeration systems, several ammonia chillers have hot gas defrost. The ammonia refrigeration world has a few different types of job opportunities. Some companies require in-house operators, but there are also external service companies, which may have a few smaller customers. In almost all cases, these jobs require technicians who can stay calm in crisis situations, as there is a lot at stake. Camron and Bryan also discuss: Recirculated vs. gravity-fed systems High vs. low-pressure receivers Dry vs. wet suction Screw compressors Copper and brass leaks Finding ammonia refrigeration companies and trade schools Find out more about TDI at tdirefrigeration.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Adolfo Wurts from Arbiter Incorporated, designer of the UEI WRS line of Bluetooth scales, comes on the podcast. We talk all about scales and how to use them. You'll want to pull a scale off your truck every time you add refrigerant to a system. Many technicians choose to estimate how much refrigerant they have to put in, and they sometimes put in more refrigerant than they estimated in their quote. Consequently, the business loses money. You'll also want to weigh your tanks during EVERY recovery to ensure that you do not overfill your recovery tanks and risk hydrostatic pressure buildup. Weighing the charge also helps keep track of amounts of increasingly uncommon and expensive refrigerants, such as R-22. Also, make sure your scales have good batteries at all times! Weighing the charge also shows you where previous technicians may have overcharged or undercharged the system to rectify a different issue. For example, someone may have starved their unit to reduce head pressure (maybe the condenser coil caused the high head pressure all along). To get the most accurate measurements possible, you must assess the quality of your scale and how you use the scale. For example, your scale must be on hard, level ground. (Do not use scales on grass; opt for concrete instead.) You should also center the tank you are weighing. However, the UEI series typically shows little variation under undesirable circumstances. (That is still not a reason to be careless with your scale.) UEI WRS scales are rugged and excellent for brutal fieldwork and inclement weather conditions. The scales also connect to smartphones via Bluetooth so that you can view the measurements remotely. The WRS series also has a wide range of design features for ease of use. You can find these scales for sale at TruTech Tools by going HERE. And don't forget to use the coupon code "getschooled" for a discount at Trutechtools.com. Find out more about the WRS line by visiting the UEI website.

In this quick announcement I talk about the launch of the revolutionary diagnostic and data management tool MeasureQuick

Todd Liles of Service Excellence Training joins the podcast. He talks about techs who shouldn't be on commission, how to make the most of your career, and facial hair profiling. Todd's skillset was mixed; he had some technical knowledge, sales experience, and communication skills. He took those skills into training, and he started his own business based on his skills; his first business didn't pan out, but he founded Service Excellence Training and has grown quite a bit. Todd develops technicians by teaching them best practices, which also boosts sales. In the past, some technicians have judged Todd because of his sales background; technicians and salespeople may have negative views of each other due to bad experiences with them. If we want technicians and salespeople to improve their lives, we need to be able to listen to each other and set aside our biases. Some technicians may resent performance-based pay and argue that it gives sales techs a motive to take advantage of others. The truth is that most of us are simply hardworking people who want to do the right thing for customers. Working for performance-based pay doesn't suddenly make them unethical. In any case, techs can maximize their value by doing best practices and benchmarking the system; collecting data will make a technician more effective and more invested in the client's system and overall best interest. When it comes to sales, facial hair profiling is very common. The clean-shaven look is a staple of sales technicians, but the training is much more important for sales success. Todd and Bryan also discuss: Service Excellence Training core truths of service Having a rough childhood and making good vs. bad choices Flat-rate vs. performance-based pay Disorganized technicians and where they might shine Dealing with paperwork Uneducated technicians vs. shysters Facial hair policies Learn more about Todd's work at servextra.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jim Bergmann returns to the HVAC School podcast to cover some advanced topics in evacuation, including rig setups and triple evacuation. To increase the speed of evacuation, you need two large-diameter vacuum hoses to overcome the limitations of pressure. Core removal is also critical, as Schrader cores are a significant restriction. It's also unwise to use a manifold for evacuation; a manifold will double your hose length, provide a restriction, and serve as a leak point. The vacuum pump is full of opportunities to expand your advanced evacuation knowledge. The pump oil needs to stay clean, and Jim recommends changing the oil after every use. When it comes to pulling the vacuum, it's worth noting that the vacuum is deeper at the pump than at the system itself. The vacuum at the pump does NOT reflect the vacuum at the system; core tools can isolate the vacuum pump from the system so that you can measure the true vacuum at the system. When we "break" with nitrogen, we're referring to nitrogen sweeps at different stages of evacuation (especially in the case of a triple evacuation). Triple evacuations are rarely necessary nowadays, but you may need to break with nitrogen from time to time. Nitrogen moves through the system so quickly that breaking with nitrogen often has a minimal impact on the vacuum. The length of evacuation doesn't really affect dehydration until you get below about 300 microns. Dehydration has more to do with the strength of the vacuum than its length. Jim and Bryan also discuss: Locking refrigerant caps Assembly lubricants Outgassing odors and gas permeability Hygroscopic vs. hydrophobic vacuum pump oil Vacuum pump oil management Average air conditioning decay rate Thermistor vacuum gauges Nitrogen regulators Metering devices Gas ballast on vacuum pumps If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Brent Ridley talks about the flame-free ZoomLock fittings and why he is using them for almost everything to replace brazing. These are tools from Parker, and they can give you leak-free fittings within seconds. ZoomLock works in residential and commercial applications. The fittings come in a wide range of sizes for the large piping of VRF systems and the smaller copper tubing of residential A/C suction lines. Brent measures the tubing to make sure there's enough room. Then, he cuts the bell end off, deburrs the copper, sands the copper down, and applies the fitting. You do NOT have to apply a lubricant or anything before you add the fitting. The fittings have two grooves to match the grooves on the jaw; that is how the fitting can crimp properly. Brent likes ZoomLock for its time-saving potential. You don't have to get your oxyacetylene (or air-acetylene) rig prepared and spend time brazing. There is also the potential to save money on the fuel and nitrogen you would use while brazing. As technology improves and the price goes down with increased production, it's possible that we can see ZoomLock-type fittings in more applications. Brazing is a key skill, but it also comes with a lot of risk to our bodies and customer property, so ZoomLock is a promising replacement for brazing. Will ZoomLock replace brazing altogether? Probably not; it would be quite difficult to use those fittings on a reversing valve, for example. But is ZoomLock a nice tool to consider for some applications? I think so. Brent and Bryan also discuss: How Brent was introduced to ZoomLock Stub lengths Oil compatibility (POE vs. mineral oil vs. refrigerant) Lateral strain on fittings Filter-driers If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jeff Neiman returns to the HVAC School podcast to explain how we can perform leak detection on a low-pressure chiller. Jeff works on systems with glycol loops or other forms of secondary fluids, which may have leaks from time to time. When the chilled water pump on the suction side runs into a vacuum, air can get into the system via the shaft seal. Then, more leaks can occur in the glycol loop as more air goes into the system. High-pressure chiller leak detection is pretty much the same as on a package unit. However, your typical low-pressure chiller will sit in a vacuum and require us to spend more time on leak detection. These low-pressure systems often have massive amounts of refrigerant below atmospheric pressure. These may have purge units that keep non-condensibles out, but some trace amounts of refrigerant can be vented out with the non-condensibles. Leaks on the low side of the system can cause even more refrigerant venting. Leak detection on the condenser side of a low-pressure chiller is pretty straightforward; like high-pressure chillers, you can use the same leak detection methods you'd usually use on a package unit or split residential system. When you know you have a leak on the low side, you can turn the chiller off; it will still be below atmospheric pressure, so you'll need to bring up the pressure to find a leak. Otherwise, you can weigh out the charge and flow nitrogen with trace amounts of refrigerant through the system. Overall, leak detection can take a LONG time on low-pressure chillers. Jeff and Bryan also discuss: High vs. low-pressure centrifugal chillers Raising the pressure on the low side Submerging leaky components in water Leaking in the tubes Pressure and its effects on gaskets Jeff's leak detection tools Open-drive motors If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode of the podcast, Jim Bergmann talks about the launch date of the measureQuick (MQ) app, what it will do, why he made it, who it is for, and why it's different than anything else that came before. MeasureQuick is a universal measurement platform that incorporates Bluetooth to display, store, and interpret measurements. The initial release focuses heavily on air conditioning, but its goal is to assist with combustion analysis and refrigeration readings. It is a troubleshooting assistant that saves time and helps technicians make sense of their readings. It combines the air side, refrigerant side, and electrical side in a single Bluetooth-connected technology. MeasureQuick helps technicians understand if the conditions are ideal for testing or if the system performs optimally while testing. The app does not automate the diagnostic process, but it is a diagnostic aid to help reduce callbacks. MeasureQuick contains both free and paid components for users, and it is backed by Testo and other sponsors. Jim Bergmann's app brings a technological appeal to the tech-savvy rising generation. MeasureQuick encourages curious technicians to understand their readings and diagnostic criteria. The goal is to modernize the HVAC industry while bringing the knowledge base of the older generation to the newer generation. Jim Bergmann's goal is to make the app TEACH its users the best practices and principles of the industry; he aims to make information accessible to technicians with varied learning preferences. This app is especially useful for those who are not avid readers. Of course, hacks who don't care about learning the correct way will always exist. However, MeasureQuick will hopefully bring accountability to our industry through education. You can find out more by going HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

James Bowman of Rectorseal returns to the podcast to discuss condensate switch codes and some best practices to comply with the codes. The humble condensate switch actually has installation standards; although there isn't a "law" about the codes, many areas follow and enforce the contents of the International Mechanical Code (IMC). Some states, including Florida, also adopt elements of the IMC and amend it to create a set of guidelines for the state. The IMC has widely-enforced code 307.2.3.1, which states that water-level monitoring devices must be installed in the primary drain pan; the device shall shut off the equipment. This code applies to downflow units and all other coils that don't have a secondary drain pan or provisions to install an auxiliary drain pan. The code also states that devices installed in the drain line are not permitted. However, code 307 is actually NOT saying that you can't install a switch in the secondary port at all; there are four different ways to comply with the code without installing a condensate switch in the primary drain pan. Switches must comply with UL 508. However, there are plenty of non-compliant switches on the market. These may even say that they "conform" to UL 508. Compliant switches will generally not short out when dropped in water, but it's up to us to make sure we're using code-compliant switches. If you're installing a float switch, be sure to follow the instructions; that's usually the best way to comply with local codes and protect the equipment. As always, make sure you test the switch before you leave the job site. James and Bryan also discuss: Mini-split drain considerations Float switches in the primary drain line Piping auxiliary floats Testing safety switches for heating equipment Drain pitch Rectorseal condensate switches Keeping redundancy in mind Condensate switches for RTU and ductless units If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Les Fork returns to the podcast to discuss on-call rotations. He explains why being on call is necessary and how you can make the most of it. We are supposed to be on call for the sake of customer service; when a customer has an emergency, it's best for the customer (and the business) when someone is available to respond to the emergency. Of course, many of us dread being on call (although the paycheck might be quite nice). You may only have one or a few techs on call, so it can be difficult to take on all of the customers each day. Although it's generally okay to speed up a bit and be less thorough, you should still be working to fix the issue at hand and tell the customer if the system needs further inspection in the future; it's also a great opportunity to propose a maintenance plan. The system should be working, the compressor should be running, and the capacitor should not be over-amping. Some companies may offer 24-hour service, and others may not. If your company offers 24-hour service, you may indeed be on call at all hours of the day and night. It makes more sense to offer 24-hour service to commercial customers, though you can certainly offer it to a residential market. Overall, it might not be best to advertise 24-hour service because you may draw in price shoppers. (You're also at liberty NOT to offer service after hours.) Les and Bryan also discuss: Managing anger and being professional Empathy Billable vs. non-billable hours Order of inspection Scheduling and prioritizing customers Walking customers through frozen coils Money talk: warranties and call-out fees Cleaning drains Tip ethics and etiquette Collecting payment If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Jim Bergmann continues talking about standard air, air density, and mass vs. volume as well as some other methods of "directly" measuring airflow. It gets pretty deep. Airflow hoods and vane anemometers can give you direct airflow measurements. You use static pressure probes, not pitot tubes, to measure TESP. When measuring static pressure, you put the negative probe in the return and the positive probe in the supply. Then, you measure the TESP (away from wiring and airflow). However, air pressure fluctuates as that air moves in the duct. Velocity pressure occurs when air moves and creates turbulence. The blower moves air, which has weight. As such, density, volume, and mass are all important as well. As air density changes, the CFM remains constant at a variable mass flow rate. When it comes to using any tool for measuring airflow, static pressure, etc., all tools are an investment of money and time; you must spend some time learning how to use those tools. You will discover those tools' limitations and must learn how to work with or around those limitations. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.